2000 def td5 won't start

I got in my car to go home tonight and turned the key all of the electrics worked and i could hear the in tank pump working but when i turned to start there was just a click from one of the relays on the bulkhead below the fuses, i got a couple of mates to push me and bump started it and got home but, when i tried it again it still won't start
Before you all say search the forum ! i already have and have since checked the negative earth and the battery which seem fine! any help ? btw i doubt its connected but i did drive rather fast through a large puddle on a farm track yesterday but have started it several times since then.

Check battery connections and starter earth ground strap

Starter solenoid? Occasionally it will start, but most times it just clicks!
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ah brilliant just had a look underneath and the smallest of the wires that goes to the starter had come off i guess it was loosened by my big splash and had fallen off this morning anyway pushed it back on and everything is good !